Right armpit pain to the upper part of the right arm may be due to muscle strain, soft tissue injury, osteoarthritis and other diseases. 1. Muscle strain: muscle strain may be caused by direct injury, such as sudden direct traction force on the muscle, or inadequate preparation before exercise. If the patient’s right muscle strain, pain, swelling, muscle spasm, muscle weakness and other symptoms, manifested in the right armpit pain to the upper part of the right arm. 2. Soft tissue injury: soft tissue injury refers to the trauma syndrome caused by direct and indirect violence to soft tissue or bone, or long-term chronic strain. Patients may experience pain and swelling in the affected area, which is manifested as pain from the right armpit to the upper part of the right arm. 3. Osteoarthritis: Osteoarthritis may be caused by obesity, inflammation, trauma and other factors, the patient may appear joint pain, limb numbness, sensory abnormalities and other symptoms, part of the patient may appear to the right armpit pain to the upper part of the right arm. There are many reasons for the right armpit pain to the upper part of the right arm, it is recommended that patients go to the regular hospital, relevant examination, so as to identify the cause of the disease.